The invention is related to a sheet-processing rotary printing press with a die cutting or punching unit and a delivery for forming processed sheets into a sheet pile or stack. Such a printing press has become known heretofore, for example, from German Patent 41 38 278, and forms sheet piles or stacks which, due to the fact that the piles or stacks being formed are of punched or die cut sheets, require careful handling in order to avoid damaging the sheets.
Thus, it is suggested particularly that sample sheets be selected and sheet pile or stack changes be performed when the printing press is stopped. In this regard, although a sample sheet may indeed be lifted off the sheet pile carefully in this way, there is a risk that this sample sheet is not representative of a given number of further sheets printed after the machine is restarted. On the other hand, in the case of a sheet pile or stack newly formed after interruption of a print run, there is a potential risk that the sheets thereof do not have the required print quality right from the beginning and that this situation will be repeated for every new pile or stack during a large print order.
It is accordingly an object of the invention, therefore, to provide a sheet processing rotary printing press with a die cutting or punching unit, and a method of operation, wherein the printing quality of a print order processed by the rotary printing press is kept constant.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method of operating a sheet-processing rotary printing press provided with a die cutting or punching unit and a delivery for forming processed sheets into a sheet pile or stack, which comprises, in a first method step, moving the punching or die cutting unit, during production printing by the rotary printing press, from a first operating state of the unit wherein the sheets are punched or die cut, into a second operating state of the unit wherein the sheets are not punched or die cut as they pass the punching or die cutting unit and, after a given number of non-punched or non-die cut sheets have passed through the unit, and in a second method step, moving the punching or die cutting unit back into the first operating state thereof.
In accordance with another mode, the method of the invention further comprises, above the sheet pile or stack, underpinning at an edge thereof a sheet that has not been punched or die cut as the sheet passes through the punching or die cutting unit after the first method step.
In accordance with a further mode, the method of the invention further comprises, in a third method step, again moving the punching or die cutting unit, after the second method step and after at least one further sheet has passed through the punching or die cutting unit, into the second operating state thereof for a time permitting a given number of sheets to pass therethrough and, in a subsequent fourth method step, moving the punching or die cutting unit back into the first operating state thereof.
In accordance with an added mode, the method further comprises, above the sheet pile or stack, underpinning the edge of a sheet that is punched or die cut as it passes through the punching or die cutting unit immediately after the fourth method step.
In accordance with another aspect of the invention, there is provided a sheet-processing rotary printing press, comprising a punching or die cutting unit operatable in a first operating state wherein sheets are punched or die cut as they pass therethrough, and in a second operating state wherein sheets are not punched or die cut as they pass therethrough; a delivery for forming the processed sheets into a sheet pile or stack; a first sheet interceptor introducible into a first interception position above the sheet pile or stack and withdrawable from the first interception position; and a second sheet interceptor introducible into a second interception position above the sheet pile or stack and withdrawable from the second interception position, the second interceptor assuming a level at the second interception position thereof which differs from a level assumed by the first sheet interceptor at the first interception position thereof.
In order to achieve the foregoing object of the invention, the rotary printing press described in the introduction hereto is thus operated in a manner that, in a first method step, the punching or die cutting unit is moved, during production or continuous printing by the rotary printing press, from a first operating state wherein the sheets are punched or die cut, into a second operating state wherein the sheets are not punched or die cut as they pass through the punching or die cutting unit, and, after a given number of non-punched or non-die cut sheets have passed therethrough, the punching or die cutting unit is moved back into the first operating state in a second method step.
In this regard, after the first method step, a non-punched or non-die cut sheet is fed in any case to a sheet pile or stack formed by the delivery, a leading edge of the sheet, for example, being interceptable in a conventional manner by a sheet interceptor, so that a pocket forms between this sheet and the sheet pile or stack, into which an auxiliary pile or stack base can be inserted for a non-stop pile or stack change. In this regard, the auxiliary pile or stack base slides along the underside of the non-punched or non-die cut sheet while punched or die cut sheets are further fed to the pile or stack, as a consequence of the second method step and the deposition of these punched or die cut sheets on the non-punched or non-die cut sheet, and damage to punched or die cut sheets is thereby avoided. To this extent, the operation according to the invention of the rotary printing press mentioned in the introduction hereto makes pile or stack changes possible during production or continuous printing without damaging the sheets, and dispensing with printing interruptions, possible on account thereof, avoids the occurrence of differences in the quality of the printed sheets of a print order even if the printing run is large.
A non-punched or non-die cut sheet deposited on the pile or stack after the first method step has been carried out can also be removed from the pile or stack as a sample sheet without damage to punched or die cut sheets if, for example, the intention is merely to check the print quality achieved by the printing press.
In a preferred development of the method according to the invention, the punching or die cutting unit, after the second method step and after at least one further sheet has passed through the punching unit, is again moved, in a third method step, into the second operating state thereof for the time it takes a given number of sheets to pass through the unit, and is moved back into the first operating state thereof in a subsequent fourth method step.
After the aforedescribed four method steps have been carried out, at least one punched or die cut sheet among the punched or die cut sheets lies at the pile or stack top side between at least one non-punched or non-die cut sheet, respectively, and this ensures that the at least one punched sheet situated between at least one non-punched or non-die cut sheet, respectively, can be drawn off from the pile or stack in the manner of a sample sheet removal jointly with these enclosing non-punched or non-die cut sheets, without damaging punched or die cut sheets.
Such removable punched or die cut and non-punched or non-die cut sample sheets permit not only the print quality to be checked but also the functioning of the punching or die cutting unit, in particular with regard to a possibly necessary correction to the punching or die cutting pressure of the punching or die cutting tools.
An advantageous preparatory step to the actual removal of the aforementioned sample sheets preferably lies in providing a sheet which is not punched or die cut as it passes through the punching or die cutting unit after the first method step and a sheet which is punched or die cut as it passes through the punching or die cutting unit immediately after the fourth method step being underpinned above the pile or stack, respectively, preferably at the leading edge of the sheets. In this way, a type of sandwich comprising at least one punched or die cut sheet lying between at least one non-punched or non-die cast sheet, respectively, is exposed in a region of mutually coordinated edges of these sheets. This sandwich can then be grasped without difficulty and removed from the pile or stack, only non-punched or non-die cut sheets being always drawn along punched or die cut sheets with the result that the latter remain undamaged.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a sheet-processing rotary printing press with a die cutting or punching unit, and a method of operation, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying single FIGURE of the drawing.
FIG. 1 is a fragmentary diagrammatic side elevational view of the sheet-processing rotary printing press according to the invention.